This invention relates to a polyurethane elastomer exhibiting superior flex fatigue properties prepared from a mixture of isocyanate-terminated polyether prepolymers and alkylthioaromatic amine curative and to a non-pneumatic tire fabricated from the elastomer.
Urethanes have been used in the manufacture of solid tires useful for such applications as industrial tires, off-the-road tires, bicycle tires and the like. They have not been entirely satisfactory in such applications because such urethane solid tires do not have the proper cushioning and handling characteristics for a soft vehicle ride on such applications as passenger vehicles. Also such solid tires suffer from internal heat build-up and subsequent degradation of the elastomer material in prolonged high speed service conditions or under rough terrain situations where the tire is being deformed.
As described in U.S. Pat. No. 4,934,425, a non-pneumatic tire exhibiting improved hysteresis and flex fatigue properties is fabricated from a resilient polyether urethane elastomeric material formed of a first isocyanate end capped low molecular weight polyether polyol having a molecular weight of between 200 and 1,500 and a second high molecular weight isocyanate end capped polyether polyol having a molecular weight between 1,500 and 4,000 cured with an aromatic diamine curative, e.g., 4,4'-methylene bis(2-chloroaniline), also referred to as MBOCA, which is preferred. While the performance of this tire is excellent, some concern has been expressed with regard to the use of MBOCA as the chain extender, or curative, for the polyurethane elastomer from which the tire body is manufactured. MBOCA is a suspected carcinogen and therefore it would be desirable to provide a polyurethane elastomer, suitable for manufacturing a non-pneumatic tire, which exhibits performance characteristics at least as good as those of the polyurethane elastomer of U.S. Pat. No. 4,934,425 but is obtained with a non-carcinogenic curative.